What to know before whitening at home.

At-home whitening is gentler than it used to be, more effective than it looks, and entirely safe at consumer concentrations — provided you know what you're working with. The kit doesn't ask many questions. This article does, on its behalf.

First, a dental check ¶

If it's been more than 12 months since your last cleaning, book one before you start. A short professional cleaning removes the layer of pellicle and tartar that peroxide would otherwise spend the first three days breaking through. The course works faster and the result is more even.

If you have any of the following, see a dentist before whitening, not just for cleaning:

• Visible cavities or chipped teeth
• Persistent gum bleeding
• Receding gums or exposed root surfaces
• A single tooth darker than its neighbours
• Recent root canal, crown, or veneer work (in the last 6 months)
• Active orthodontic treatment

Fillings, crowns, veneers ¶

This is the most important sentence in the article: whitening does not bleach restorations. Fillings, crowns, veneers, and bonded composite are colour-fixed at the time they were placed. They stay that exact shade through any whitening course.

If you have a visible composite filling on a front tooth and you whiten the rest 4 shades lighter, the filling will look noticeably darker afterward. The right order is: whiten first, wait two weeks for the shade to stabilize, then have any visible restorations matched to the new shade. This is dentistry-standard practice and a thirty-minute appointment.

Take a baseline shade ¶

Before you start, take a single photograph of your front teeth in natural light against a neutral background (a white wall is fine). Lips relaxed, no smile-stretch. Save the date in the filename. Take the same photo on day 7, day 14, and one month after finishing.

Without this, you'll under-credit the work. The eye adapts day by day. The photographs don't.

The week before — sensitivity preload ¶

Most reported sensitivity from at-home whitening is preventable with one week of preparation. See the full sensitivity protocol, condensed here:

• Switch to a potassium-nitrate toothpaste 7 days before starting.
• Add a fluoride or hydroxyapatite mouth rinse at night.
• If you're using a medium-bristle brush, switch to soft now.
• Avoid sparkling water and citrus the day before day one — both temporarily soften enamel.

Day one — a calm protocol ¶

1. Brush, but lightly. Do not whitening-toothpaste before whitening. Plain fluoride or hydroxyapatite, soft brush, 90 seconds.
2. Spit, dry the front face of your teeth with a tissue. Strips adhere better to a dry tooth.
3. Apply the strip / tray. Press firmly along the front face. Smooth out any air bubbles with a finger.
4. Wear for the stated duration — usually 30 minutes for strips. Less is fine. More is not better.
5. Remove gently. Rinse the mouth with lukewarm water. Do not eat, drink anything pigmented, or brush for 30 minutes.
6. Do not double the dose on day one to "see results faster." It only buys you sensitivity.

After the 14 days ¶

Shade stabilises over 7 to 14 days following the last session. Don't judge the final result on day 14. Photographs taken on day 21 are the honest measure.

To hold the result:

• Continue using a low-RDA, fluoride or hydroxyapatite toothpaste.
• Drink water alongside coffee and red wine. End meals with cheese or water.
• One top-up strip every 4–6 weeks holds most of the gain, or a 3-day mini course twice a year.
• Don't whiten continuously. Enamel needs recovery windows.

If you shouldn't whiten right now ¶

Some cases where the right answer is "not yet":

• Pregnancy or breastfeeding — limited evidence is available; the precautionary practice is to wait.
• Under 18 — at-home consumer whitening is not generally recommended for developing teeth.
• Active gum disease, untreated cavities, fresh dental work — treat the cause first.
• Severe enamel erosion or chronic acid reflux — whitening on weakened enamel can worsen sensitivity.
• If you tried whitening within the last 6 weeks — your teeth need a recovery window.

The cleaner you start, the faster the course works.

Next, the editorial: oral cosmetics, as a category — why dental care is becoming more like skincare.